diff --git a/build/isnearupgrade.go b/build/isnearupgrade.go
index 4273f0e9e3f..74975780fe1 100644
--- a/build/isnearupgrade.go
+++ b/build/isnearupgrade.go
@@ -5,5 +5,8 @@ import (
 )
 
 func IsNearUpgrade(epoch, upgradeEpoch abi.ChainEpoch) bool {
+	if upgradeEpoch < 0 {
+		return false
+	}
 	return epoch > upgradeEpoch-Finality && epoch < upgradeEpoch+Finality
 }